Conventionally, in the production of semiconductor devices, fine processing by lithography using a photoresist has been performed. The fine processing is a processing method for forming fine convexo-concave shapes corresponding to the following pattern on the surface of a substrate by: forming a thin film of a photoresist on a semiconductor substrate such as a silicon wafer; irradiating the resultant thin film with an active ray such as an ultraviolet ray through a mask pattern in which a pattern of a semiconductor device is depicted for development; and subjecting the substrate to etching processing using the resultant photoresist pattern as a protecting film. Recently, however, the high integration of semiconductor devices has progressed and the adopted active ray tends to have a shorter wavelength, such as an ArF excimer laser (193 nm) replacing a KrF excimer laser (248 nm). Following such a tendency, the influence of reflection of an active ray on a semiconductor substrate has become a large problem. Thus, in order to solve this problem, widely studied is a method of providing a bottom anti-reflective coating between the photoresist and the substrate. For such a bottom anti-reflective coating, many investigations on an organic bottom anti-reflective coating composed of a polymer having a light absorbing group and the like are performed due to easiness of its use and so on. Examples of the bottom anti-reflective coating include: an acrylic resin-based bottom anti-reflective coating having both a hydroxy group as a crosslinkable group and a light absorbing group within a single molecule; and a novolac resin-based bottom anti-reflective coating having both a hydroxy group as a crosslinkable group and a light absorbing group within a single molecule.
Characteristics required for the bottom anti-reflective coating include a large absorbance to light or radiation, no intermixing with a photoresist (being insoluble in a photoresist solvent), no diffusion of low molecule substances from the bottom anti-reflective coating to the photoresist as an upper layer during heating-baking, a dry etching rate higher than that of the photoresist, and the like.
Used as an underlayer film between the semiconductor substrate and the photoresist is a film known as a hardmask containing a metal element such as silicon and titanium. In this case, the resist and the hardmask have components largely different from each other, so that the removal rates of the resist and the hardmask by dry etching largely depend on the type of a gas used for dry etching. Then, by appropriately selecting the type of a gas, the hardmask can be removed by dry etching without a large decrease in the film thickness of the photoresist. Thus, in the production of semiconductor devices in recent years, for achieving various effects such as the reflection preventing effect, resist underlayer film is disposed between the semiconductor substrate and the photoresist. Although the studies of a composition for a resist underlayer film have been performed, the development of a novel material for the resist underlayer film is desired due to the diversity of characteristics required and so on. As one of such materials, there is mentioned a polysiloxane.
There is disclosed a silica-based coating film forming composition containing a polysiloxane, a solvent, and acyclic basic compound (Patent Document 1).
On the other hand, it is known that a polysiloxane has organic groups and the organic group is substituted with various functional groups to exert functions thereof. For example, there is disclosed a coating composition using a polysiloxane having a sulfonic acid group as a hydrophilic group and having reflection preventing characteristics and clouding preventing characteristics (Patent Document 2).